Current discrete high frequency optical tracking systems utilize dc bias and a narrow-band tuned detector signal preamplifier. This improves signal-to-noise ratio and helps prevent amplifier saturation. To counter this system, it is necessary only to transmit to the detector a similar or greater power level of light modulated at the same frequency. Hence, it is desirable to be able to use any of a wide range of modulation frequencies, selected at random, to make possible countermeasures much more difficult. One current method of receiving this greater range of frequencies is to use a wide-band detector preamplifier. With this method, however, noise and saturation are critical problems.